Research findings about the etiology of learning disorders suggest they are multifactorial, but according to the text it is generally believed that

A) psychological causes may be implicated.
B) biological causes may be implicated.
C) neither biological nor psychological causes are likely to be implicated.
D) biological causes may be implicated, but secondary to psychological causes.
E) both biological and environmental causes may be implicated.

Research findings suggest that learning disorders are caused by a combination of biological and environmental factors, making them multifactorial. Factors such as genetics, brain structure and function, and environmental influences have all been identified as potentially contributing to learning disorders. Psychological factors may also play a role in some cases, but they are not the only cause. Therefore, options A, B, D, and C are not the best choices as they either only mention one type of cause or exclude one type of cause altogether. Option E, which acknowledges the role of both biological and environmental factors, is the most accurate choice.